Momentary switch latched relay

[TaDa]

I'm thinking of making a 6v momentary switched circuit that controls relay on in a separate 20v circuit.
The relay needs to be on an isolated circuit to the momentary switch circuit (which I plan to run on batteries). See attached pic (apologies for the quality)
I think the flip flop IC of choice is a 4013 flip flop which will latch on/off with the presses on the momentary switch.

But
What is a suitable opto isolator to switch 20V?
Is the 4013 appropriate?
Is there any way I can guarantee it will startup 'on'?
Is there a way to wire in another switch that will switch it to the 'on' state - regardless of which state it is in?

 

[MikeMl]

I would use two buttons, one for ON and the other for OFF, sort of like a motor controller or some desk lamps. That way, you do not need a battery, flip flop or opto-isolator. Use a standard "hold-in latching relay" circuit, with a Normally-Open mom. push switch to start it, and a Normally-Closed mom. push switch to unlatch the relay.

 

[crutschow]

You could use a small solid-state DC relay such as this for the opto isolator.

To turn it ON, apply a momentary logic high to the SET input. To insure it's ON from power on, add a cap between Vdd and the SET input with a resistor from the SET input to ground. A value of 0.1uF and 1 megohm should work.

 

[ljcox]

You could build a relay flip flop. See attachment.

 

[KMoffett]

Another relay possibility: **broken link removed**

Ken

 

[TaDa]

Thanks for all the answers.
I really only want one momentary button
I'm intrigued by the solid state relay but because of concerns about the mains related aspects of the 20V supply I want to have these two circuits well and truly separated
So I want to stick with the 4013 and the opto isolator.

Can anyone recommend an opto isolator that'll work at 5v on the controlling side and 20V on the driven side?

And whether I can bias the 4013 to default to 'on'?

 

[Boncuk]

Hi TaDa,

you need to connect three state monostable circuits to the outputs of the 4013.

Otherwise the latching relay would be worthless and you could as well use a normal relay.

A latching relay requires short pulses to throw contacts from NC to NO and vice versa.

For an optocoupler check out the 6N139. It can stand a max VCC of 18V and requires 0.5mA forward current for the transmitter.

Vee might be as high as you require since the output transistor (open collector) can source 50mA.

Boncuk

 

[Reloadron]

Not quite the coil voltage you want but you may want to consider an impulse relay similar to this family of relays. An impulse relay like this would give you the one button push on / off you seem to be looking for.

Ron